There are several ways to assess the quality of a spatial network. We chose to use the concept of network efficiency which is, essentially, a comparison between the spatial distance and the shortest path. The efficiency in the communication between two nodes \(i\)  and \(j\) , \(E_{ij}\)  corresponds to the ratio between the spatial distance and the shortest path length, \(E_{ij} = d_{ij}/l_{ij}\) , commonly known as detour index or route factor [1]}. By computing the average over all pairs of nodes we obtain the global efficiency as proposed in [2]}, (despite an alternative definition has been given in [3]}):
\(E_{\text{glob}}= \frac{1}{N\left( N-1\right)} \sum _{i\ne j} \frac{d_{ij}}{l_{ij}} \,.\) 
